1. Field of the Invention
The invention relates to a dispenser for dispensing metered amounts of liquid or paste-like products. The dispenser comprises a cylindrical reservoir open at the bottom. The open bottom end is closed by an axially movable plunger. The dispenser further comprises a dispensing head arranged on the reservoir. The dispensing head comprises a bell-shaped dispensing pump with elastic sidewalls. The dispensing pump forms a closed pump chamber together with an intake valve and an outlet valve arranged in the pump neck.
2. Description of the Related Art
For dispensing metered amounts of liquid or paste-like (pasty) products, different devices are known for pressing the product out of the reservoir and through an application opening. These devices differ significantly with respect to their configuration as well as their function.
A dispenser of the aforementioned kind is known from European patent 0 048 420 B1. The dispenser is comprised of a hollow reservoir of a cylindrical shape with an open end at the bottom end which is closed by an axially movable tracking plunger. The upper end of the reservoir has a cover with an intake valve. A dispensing head is arranged on this cylindrical reservoir and comprises a dispensing pump arranged in the dispensing head whose pump chamber is limited at the intake side and at the exit side by a check valve. A mouthpiece with an application opening is arranged downstream of the dispensing pump.
For a metered dispensing of the product to be dispensed, a downwardly acting pressure is applied onto the dispensing pump causing the dispensing pump to be compressed, the outlet valve to be opened, and the intake valve to be closed so that the product contained within the pump chamber is forced out via the application opening of the mouthpiece.
Upon releasing and subsequent relaxation and expansion of the dispensing pump, the outlet valve is closed and the intake valve opened. The under pressure or vacuum which is generated in the pump chamber when the dispensing pump expands now causes new product to be taken in from the reservoir through the intake valve of the cover wherein at the same time the plunger or the closure is moved farther in the direction toward the cover. This process can be repeated until the reservoir is empty and the tracking plunger contacts the cover.
A common feature of such dispensers is that after emptying they generally cannot be refilled but must be disposed of. Therefore, a general and important requirement in this connection is that the product “disposable dispenser” can be manufactured as inexpensively and simply as possible. This holds true, in particular, for the complex construction parts contained within the dispenser, for example, the check valves whose valve flaps are mechanically loaded and must work properly during the entire service life of the dispenser. The check valves are often positioned at locations of the dispenser that are not easily accessible so that the attachment of the valve flaps, usually by riveting, is often difficult and expensive.